The present invention relates to a tire pressure monitoring system and a method for monitoring air pressure within a pneumatic tire of a vehicle. More particularly, the present invention relates to a tire pressure monitoring system that includes a tire pressure gauge for use in adjusting the air pressure within a tire and a method of using the system.
Tire condition monitoring systems, and more particularly tire pressure monitoring systems, are becoming increasingly more popular. Such monitoring systems alert a vehicle operator when a tire condition falls outside of a predetermined range. For example, when monitoring a tire pressure with a tire pressure monitoring system and where the desired tire pressure range is 32-38 psi, the system will alert the driver of a low air pressure condition in response to the air pressure within the tire dropping below 32 psi.
Tire condition monitoring systems assist vehicle operators in maintaining proper inflation pressure within their vehicle tires. Proper inflation pressure results in reduced tire wear, increased vehicle fuel efficiency, and many other positive attributes. Additionally, many vehicle suspension systems are designed for use with tires meeting particular specifications. One of the tire specifications is the tire inflation pressure. Thus, proper inflation pressure may result in a more comfortable and sometimes a safer vehicle ride.
Known tire condition monitoring systems include a tire based device for sensing a tire condition, such as air pressure within a tire. The device transmits signals indicative of either the actual air pressure within the tire or an alert condition when the air pressure within the tire is outside of the predetermined range. A vehicle based controller receives the transmitted signals. A display or other indicator is operatively connected to the vehicle based controller for alerting the.vehicle operator when an alert condition arises.
Copending patent application Ser. No. 09/687,709, filed Oct. 12, 2000 and assigned to the assignee of the present invention discloses a tire condition monitoring systems having an associated antenna wired into each wheel well of the vehicle. Each antenna is operable to send a low frequency signal to an associated tire based device to initiate tire condition monitoring. The tire based device responds to the low frequency signal with a radio frequency signal indicating a sensed tire condition and a tire identification code. The location of each tire on the vehicle is determined by matching the known location of the antenna sending the low frequency signal with the identification code from the tire based device responding to the low frequency signal.
When a tire condition monitoring system indicates an alert condition, such as a low pressure condition, the vehicle operator should take appropriate remedial actions, such as adding air to the appropriate tire to bring the pressure within the desired range. Unfortunately, many vehicle operators do not carry air pressure gauges in their vehicles and many air pressure gauges that are supplied at service stations are inaccurate. Thus, a need exists for an accurate and reliable air pressure measuring system and method for indicating that the air pressure within the tire has come within the desired pressure range during the filling process by the vehicle operator or service technician.
The present invention relates to a tire inflation pressure monitoring system for monitoring air pressure within a tire. The tire pressure monitoring system comprises a tire based unit for sensing air pressure within the tire and for transmitting a pressure signal indicative thereof. The system also comprises a vehicle based unit for receiving the pressure signal and for comparing the pressure signal to a predefined pressure range. The vehicle based unit is operable in one of (i) a normal operating mode and (ii) a pressure gauge operating mode. The vehicle based unit when operating in the normal operating mode outputs an alert signal in response to the air pressure within the tire being outside of the predefined pressure range. The vehicle based unit when operating in the pressure gauge operating mode outputs an in-range signal in response to the air pressure within the tire being within the predetermined pressure range. The system also comprises a switch and at least one indicator. The switch, when actuated, changes the operating mode of the vehicle based unit. The at least one indicator is operatively connected to the vehicle based unit and becomes energized in response to receipt of the alert signal when the vehicle based unit is in the normal operating mode and becomes energized in response to the in-range signal when the vehicle based unit is in the pressure gauge operating mode.
In another aspect, the present invention relates to a method of monitoring air pressure in a pneumatic tire. During the method, an operating mode for a vehicle based unit of a tire pressure monitoring system is ascertained. The vehicle based unit has a normal operating mode and a pressure gauge operating mode. The air pressure within the tire is sensed with a tire based unit and the tire based unit provides a pressure signal indicative of the pressure within the tire to the vehicle based unit. The pressure signal is compared to a predetermined pressure range. An alert signal is output to an indicator in response to the vehicle based unit being in the normal operating mode and the air pressure being outside the predetermined pressure range. An in-range signal is output to the indicator in response to the vehicle based unit being in the pressure gauge operating mode and the pressure signal being within the predetermined pressure range.